Catalytic removal of hydrogen sulphide from liquid sulphur

ABSTRACT

The invention is an improved catalytic process for removing H 2  S and sulfanes from liquid sulfur and a catalyst system for carrying out the process. The catalyst comprises a basic component and a surfactant component.

The invention is a process for the quick removal of H₂ S present inliquid sulfur in a dissolved state alone or with hydrogen polysulfides.The invention is also a catalytic system that can be used for carryingout the process.

BACKGROUND OF THE INVENTION

Large quantities of sulfur are produced by the CLAUS process by reactinghydrogen sulfide originating, for example, from deacidification ofnatural gas or from treatments of petroleum products with the sulfurdioxide formed, for example, by combustion of H₂ S or also by combustionof sulfur or sulfur-containing compounds such as pyrites, according tothe reaction:

    2H.sub.2 S+SO.sub.2 ⃡3S+2H.sub.2 O

A substantial fraction of the sulfur produced by the CLAUS process isstored in the liquid state in heat-insulated tanks, then transported inliquid form to the places of use by utilizing transportation means suchas tank trucks, tank barges, tank cars, or also pipelines provided withadequate heat-insulating means that allow the sulfur to remain liquidduring the transportation.

The liquid sulfur obtained by the CLAUS process always contains a smallamount of dissolved H₂ S and hydrogen polysulfides, also calledsulfanes, of the formula H₂ S_(x) wherein x represents a number equal toor more than 2. The sulfanes slowly decompose as time passes, releasingH₂ S. The gaseous phase above the liquid sulfur in the storage tank orin the container used for its transportation includes, therefore, acertain proportion of H₂ S, which, due to the toxicity of the gas andits tendency to spontaneous inflammation, makes the operationsassociated with the loading and unloading of the containers that servefor the transportation of the liquid sulfur dangerous. In order thatthese operations can be performed safely, the CLAUS liquid sulfur isgenerally subjected, prior to storage and transportation, to agas-removal treatment, the purpose of which is to lower the content offree and combined H₂ S of the liquid sulfur below a threshold that thepractice has determined to be 10 ppm.

The total amount of H₂ S and of sulfanes in the CLAUS liquid sulfur isgenerally comprised between 50 and 700 ppm and generally depends on theconcentration of H₂ S in the gaseous phase above the liquid sulfur andon the temperature of liquid sulfur. In addition, the relativeproportions of free H₂ S and sulfanes dissolved in the liquid sulfurdepend also on the temperature of the liquid sulfur.

The process of removal of the H₂ S present in the liquid sulfur in freeand combined forms includes two phases, a first phase in which thesulfanes are decomposed according to the reaction H₂ S_(x) →H₂ S+S_(x-1)and a second phase in which the released and simply dissolved H₂ S andthe light sulfanes are separated from the liquid sulfur.

The decomposition of the sulfanes to H₂ S and sulfur is a slow reaction.The rate of removal of the H₂ S and light sulfanes is limited by thespeed of the decomposition reaction.

Most of the processes suggested for removing the free and combined H₂ Sdissolved in the liquid sulfur, are of the type in which a catalyticsystem formed by one or more compounds consisting of ammonia orcompounds that release ammonia, or compounds having a basic character inthe sense of BRONSTEDT are added to the sulfur. The catalyst systemfacilitates the decomposition of the sulfanes, the released H₂ S beingsimply dissolved in the sulfur is separated from the liquid sulfur byany technique that allows the H₂ S dissolved physically to escape fromthe liquid sulfur or to be transformed in situ to sulfur under theaction of an oxidizing gas. In particular, in the process disclosed inEP-0045636, the catalytic system consists of a compound selected frominorganic compounds of phosphorus, urea, urea derivatives, dithionates,dithionites, thiosulfates, bisulfides, and bisulfites. In the processesdescribed in U.S. Pat. No. 3,364,655, FR 2,159,691 and U.S. Pat. No.4,131,437, ammonia is used as the catalyst and the H₂ S released bydecomposition of the sulfanes is removed by atomizing the liquid sulfur(U.S. Pat. No. 3,364,655), by stripping with an inert gas(FR-2,159,691), or by sweeping the open surface of the liquid sulfur bymeans of a gas such as water vapor, nitrogen, air or residual gas from asulfur plant (U.S. Pat. No. 4,131,437). The use of a catalytic system ofthe type which utilizes ammonia, ammonium salts, amines and othernitrogenous compounds has also been proposed in FR 2,185,587 and U.S.Pat. No. 3,447,903 with transformation in situ to sulfur of the H₂ Sreleased by decomposition of the sulfanes by the action of an oxidizinggas, namely, air, in the first case and SO₂ in the second case, injectedinto the liquid sulfur.

The above cited processes have the inconvenience of slow reaction rateswhich hinder carrying out the process continuously at the exit from asulfur manufacturing process. In effect, the processes disclosed requireseveral hours, for example, at least 2.5 hours when using a catalyticsystem formed by the compounds disclosed in EP-0045636, or at least from5 to 8 hours when using ammonia as the catalytic system to obtain aliquid sulfur having a content of free and combined H₂ S below the levelrequired by the standards (10 ppm).

BRIEF DESCRIPTION OF THE INVENTION

It has now been discovered that it is possible to improve the activityof the compounds of basic character used as catalysts in the processesfor removal of free and combined H₂ S present in the liquid sulfur byadding to the mixture of liquid sulfur and catalyst at least onesurfactant compound. The addition of surfactant reduces the duration oftreatment of the liquid sulfur and overcomes the problems of acontinuous process. In addition, the amount of catalyst required in themodified process needed to bring the H₂ S content of the liquid sulfurto the desired value below the threshold level is sufficiently smallthat it does not significantly increase the ash content of the treatedsulfur.

The invention is a process for rapid decomposition and removal of H₂ Spresent in the liquid sulfur, either in a simply dissolved state orcombined as hydrogen polysulfides, of the type wherein a catalyticsystem containing one or more compounds of basic character is admixedwith the liquid sulfur and the liquid mixture is maintained at anelevated temperature to remove the hydrogen sulfide from the liquidsulfur, characterized in that said catalytic system includes at leastone surfactant compound.

The catalyst component comprising the basic compound or compounds andthe component comprising the surfactant compound or compounds, can beadded to the liquid sulfur either separately or in the form of apre-formed mixture. In a preferred embodiment of the process accordingto the invention, the catalytic system added to the liquid sulfurcomprises one or more compounds, each one having a basic character andsurfactant properties.

The amount of catalytic system added to the liquid sulfur should besufficient to obtain rapid removal of the H₂ S and, not be so high as tosignificantly increase the ash content of the liquid sulfur. The amountof catalytic system added to the liquid sulfur is preferably betweenabout 0.5 and 60 ppm based on the weight of sulfur.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of an embodiment of a process ofthe invention utilizing a mechanical mixing zone and one spray zone.

FIG. 2 is a diagrammatic representation of an embodiment of the processof the invention utilizing a mechanical zone and two spray zones.

DETAILED DESCRIPTION OF THE INVENTION

When the catalyst system added to the liquid sulfur is a two-componentsystem, the compound or compounds of basic character that constitute oneof the components of said catalyst system are selected from compounds ofbasic character in the sense of BRONSTEDT, which are stable in theliquid sulfur at the operation temperature or change at this temperatureinto a stable basic compound. The basic compounds can be in particularhydroxides of akali metals or alkaline-earth metals such as sodium,potassium or calcium, compounds such as ammonia, hydrazine,hydroxylamine, aliphatic or cyclic amines of the primary, secondary ortertiary type, compounds such as urea or thiourea and derivativesthereof, basic heterocyclic compounds, weak acid salts of strong bases,quaternary nitrogenous compounds that decompose at operatingtemperatures to yield ammonia or an amine. The basic compounds definedas catalysts in EP 0045636 and U.S. Pat. No. 3,447,903 are also suitableas the basic component of the catalytic system according to theinvention.

Another preferred form of the basic component are heterocyclicmonocyclic and heterocyclic polycyclic compounds that contain at leastone nitrogen heteroatom . In addition to the nitrogen heteroatom, theheterocyclic compounds can contain other heteroatoms, such as sulfurand/or oxygen. The useful basic compounds are soluble and stable in theliquid sulfur at temperatures of treatment and have a boiling pointabove about 200° C. at atmospheric pressure The heterocyclic compoundsbeing proposed as catalysts for the removal of the H₂ S contained in theliquid sulfur in a patent application filed by the applicants at evendate with this patent application are useful in the present process. Theproposed catalysts include by way of examples, heterocyclic compoundssuch as quinoline, isoquinoline, benzoquinoline, acridine, benzacridine,quinoxaline, quinazoline, phenazine, phenantridine, phenantrolines,naphthyridines, bipyridyls. The patent application, Ser. No. 171425 isincorporated herein by reference.

As used herein, the phrase heterocyclic monocyclic compounds refers toheterocyclic compounds having only one ring, the ring having at leastone heteroatom incorporated thereon. The heterocyclic monocycliccompounds can have substituents appended to the heterocyclic ring. Thephrase heterocyclic polycyclic compounds, as used herein, refers tocompounds having two or more cyclic moieties, which may be attached orfused, in which at least one of the cyclic moieties is a heterocyclicmoiety having at least one heteroatom incorporated in the ring.Preferably two or more of the cyclic moieties are heterocyclic moietiesin the polycyclic compound. The heterocyclic polycyclic compounds canhave substituents appended thereto as long as the substituents do noteliminate the catalytic activity of the compound.

The surfactant compounds that are useful to form the surfactantcomponent of the two-component catalytic system can be anionic,non-ionic, cationic or amphoteric surfactant compounds. Particularlyuseful surfactant compounds of the two-component catalytic system can beformed from one or more surfactant compounds selected from thesurfactant compounds having little or practically no basic charactersuch as anionic or non-ionic surfactant compounds and in particular theoxyethylated mercaptans, oxyethylated phenols, glycol polyethyleneesters, derivatives of oxyalkylamides and polyethoxyesters of fattyacids. The surfactant component can be one or more cationic surfactantcompounds, that is, surfactant compounds having a certain basiccharacter.

The basic component and the surfactant component, the association ofwhich forms the two-component catalyst system added to the liquid sulfurare used in proportions such that the amount of basic componentpreferably represents from 0.05 to 50%, and more preferably from 0.2 to20%, of the total weight of said components.

When the catalytic system added to the liquid sulfur is a singlecomponent, that is, formed by one or more compounds each having a basiccharacter and surfactant properties, said catalytic system preferablycomprises one or more compounds selected from amino surfactant compoundsand especially fatty amines, fatty alkylene diamines, salts and inparticular the hydrochlorides and carboxylates of such fatty amines anddiamines, the oxyalkylated derivatives of said fatty amines and diaminesand the salts thereof, the quaternary ammonium compounds of fatty chainsand the benzalconium salts. The phrase amino surfactant compound refersto compounds which have an amino group, have basis in the BRONSTEDTsense and have surfactant properties.

Among said amino surfactant compounds, the following are particularlyuseful in the practice of the present invention:

fatty amines of the formula ##STR1## and salts thereof, especiallyhydrochlorides and carboxylates,

alkylene diamines of fatty chains of the formula R--NH--C_(m)H_(2m))--NH₂ and salts thereof, especially hydrochlorides andcarboxylates,

oxyalkylated derivatives of fatty amines and fatty alkylene diamineshaving the respective formulae ##STR2##

quaternary ammonium compounds containing fatty chains of the formula##STR3##

benzalconium salts of the formula ##STR4## with R representing in theseformulae an alkyl or alkenyl radical of from C₈ to C₂₂, R₁ and R₂,identical or different, each one designating an R radical hydrogen atom,or an alkyl radical of from C₁ to C₄, R₃, R₄ and R₅, identical ordifferent, representing each an R radical or an alkyl radical of from C₁to C₄, R₆ and R₇, identical or different, designating an alkyl radicalof from C₁ to C₄, m, n, p and q representing integers of from 1 to 4inclusive, x, y and z being numbers of from 1 to 10 inclusive and X⁻ andY⁻ designating salifying anions, especially Cl⁻ or carboxylates, such asfor example, acetate.

The oxyalkylated derivatives of fatty amines and fatty alkylene diaminesare preferably those corresponding to the formulae ##STR5## wherein R,x, y and z have the meanings given above.

The temperatures for carrying out the process according to the inventioncan vary very broadly above the melting point of the sulfur, forexample, between about 125° C. and about 180° C. Preferably the processis carried out at temperatures of from about 130° C. to about 165° C.

The process according to the invention is carried out in a manner suchthat the catalytic system is distributed throughout the mass of liquidsulfur preferably in a homogeneous manner. The process is also conductedin a manner that permits hydrogen sulfide released by decomposition ofthe sulfanes and present in a dissolved state in the liquid sulfur to beseparated from the liquid sulfur. The liquid sulfur containing thecatalytic system can be subjected to stirring by any suitable mechanicalsystem of stirring, the released H₂ S naturally escaping from the massof liquid sulfur. The stirring of the liquid sulfur and the escape ofthe released H₂ S can also be carried out by stripping by means of aninert gas. As used herein, an inert gas is a gas which does not reactwith the constituents of the medium in which it is introduced under theconditions of temperature selected for carrying out the process,preferably the stripping gas is nitrogen, CO₂, air, water vapor,residual gas from a sulfur recovery plant, or mixtures of said gases.The stirring of the liquid sulfur that contains the catalytic system andthe removal of the released H₂ S can likewise be effected by subjectingthe liquid sulfur to an atomization or spraying such as described, forexample, in U.S. Pat. No. 3,364,655. If necessary, the process can becarried out using a combination of these different modes of contactingthe liquid sulfur with gas to eliminate the released H₂ S.Countercurrent contact of the sulfur with an inert gas in a column canalso be useful.

The treatment of the liquid sulfur that includes one, or a combinationof the above-mentioned operations is generally effected in aheat-insulated vessel, for example, a metal tank or reservoir, whereinsaid liquid sulfur is stored.

It is preferred to sweep the vapor space above the open surface of theliquid sulfur in a storage tank, by means of an inert gas such as CO₂,nitrogen, air, residual gas of a CLAUS sulfur plant to remove the H₂ Sto an incineration zone and thus facilitate the removal of the H₂ Sreleased by decomposition of the sulfanes away from the mass of liquidsulfur. When the sweeping operation is effected by means of a residualgas from a sulfur plant that is, of a gas still containing a smallamount of H₂ S, said amount must be controlled, for example, by dilutingThe residual gas with an inert gas, in a manner such that, at leasttoward the end of the operation, the concentration of H₂ S in thesweeping gas is not above the content of gaseous H₂ S in equilibrium, atthe temperature of the operation, with the amount of H₂ S tolerated inthe liquid sulfur.

The catalytic system can be added to the liquid sulfur all at one timeat the beginning of the operation or by fractions throughout theoperation. When the treatment for elimination of H₂ S includes amechanical agitation of the liquid sulfur contained in a metal vessel,tank, or reservoir where it is stored, the catalytic system can be addedto the liquid sulfur entering the vessel serving for the treatment. Ifstripping is considered for eliminating the H₂ S from the mass of liquidsulfur, the catalytic system can be introduced in the stripping gasand/or added during the feeding of liquid sulfur to the treating vessel.In case an atomization or spraying of the liquid sulfur is effected,such an atomization generally includes the introduction of the liquidsulfur in an atomizing or spray nozzle by means of a pump, including asuction conduit immersed in the liquid sulfur.. The catalytic system canbe introduced into the pump suction or discharge and/or with the feed tothe vessel for treatment of the liquid sulfur.

The process according to the present invention can be carried outbatchwise or continuously.

FIGS. 1 and 2 of the enclosed drawing diagrammatically show two devicesthat can be used for carrying out the process according to theinvention.

The process according to the invention with atomization of the liquidsulfur containing the catalytic system can be carried out batchwise forexample, as shown in FIG. 1 by operating in a heat-insulated closedvessel 1, preferably a metal tank or reservoir divided into twocompartments, namely, a first compartment 2 of small volume and a secondcompartment 3 of considerable volume, by a partition 4 open at the upperpart so as to form an overflow allowing the liquid sulfur to flow fromthe first into the second compartment. The bottom 5 of the firstcompartment is raised in relation to bottom 6 of the second compartment.The vessel is provided with an inlet 7 for sweeping gas that enters thefirst compartment above the level of the sulfur and an outlet 8 forsweeping gas provided in the upper part of the second compartment. Thefirst compartment is provided with a conduit 9 for introducing liquidsulfur, said conduit being in fluid communication with line 10 foradding the catalyst system, and equipped with mechanical means 11 foragitation, and the second compartment is equipped with a system 12 forspraying including a pump 13 whose suction conduit 14 is adapted to besubmerged in the liquid sulfur and the discharge 15 is connected to aspray nozzle 16 situated in said second compartment so as to be placedabove the open surface 17 of the liquid sulfur contained in thiscompartment.

In such a manner of carrying out the process, the liquid sulfur thatcontains the catalytic system is subjected to strong agitation in thefirst compartment 2 which distributes the catalytic system in the liquidsulfur contained in said compartment to initiate the decompositionreaction of the sulfanes, then the mixture of liquid sulfur andcatalytic system flows by the overflow 4 into the second compartment 3in which said mixture is subjected to spraying or atomization. The H₂ Sthat escapes from the mass of liquid sulfur contained in the twocompartments is removed by circulation of the sweeping gas, for example,a residual gas from a CLAUS sulfur plant and carried by the gas to anincineration zone. When the H₂ S content of the liquid sulfur has beenreduced to the required level, the liquid sulfur can be pumped fromcompartment 3 through conduit 51.

The process according to the invention can be carried out continuouslywith spraying or atomization of the liquid sulfur containing thecatalytic system, for example, as shown in FIG. 2, by operating in aheat-insulated closed vessel 20 such as a heat-insulated metal reservoirdivided into at least three successive compartments namely, an inletcompartment 21, one or more intermediate compartments 31 and an outletcompartment 41, by parallel vertical partitions 22 and 32 which are openat the lower part for connecting each one of the compartments with thecompartments that are adjacent, said partitions being of a height lesserthan that of the vessel so as to be able, should that be the case, topermit overflow of the liquid sulfur. The inlet compartment 21 isprovided with a conduit 23 for introducing the liquid sulfur. Theconduit 23 is in fluid communication with a conduit 24 for adding thecatalytic system. Vessel 20 in its upper part has an outlet 25 for asweeping gas, and is equipped with a mechanical agitation system 26.Each of the intermediary compartment(s) 31 and the outlet compartment 41are equipped with an atomization or spray system 33 and 43, said systemincluding a pump 34 and 44 with suction conduits 35 and 45 adapted tosubmerge in the liquid sulfur in the downstream part of the compartmentconcerned and, with discharge conduits 36 and 46 connected toatomization or spray nozzles 37 and 47 placed in said compartment in theupstream part of the compartment above the open surface 30 of the liquidsulfur it contains. In addition, the outlet compartment 41 is providedwith an inlet 48 for a sweeping gas arranged above the open surface 30of the liquid sulfur and the pump of the spray system in saidcompartment communicates with a conduit 49 that serves to remove thetreated liquid sulfur.

In such a manner of carrying out the process, the liquid sulfur with theadded catalytic system continuously arrives at the inlet compartment 21and is there subjected to vigorous agitation which leads to ahomogeneous distribution of the catalytic system in the liquid sulfurcontained in said compartment, to initiate decomposition reaction of thesulfanes, then the mixture of liquid sulfur and catalytic system flowscontinuously and successively into the intermediary compartments 31,then into the outlet compartment 41, said mixture being subjected to aspraying in each one of said compartments The H₂ S that escapes from themass of liquid sulfur contained in the different compartments iscontinuously removed from the vessel mixed with the sweeping gas such asa residual gas of a CLAUS sulfur plant which is injected into the outletcompartment 41 and circulates above the open surface 30 of the liquidsulfur countercurrent to the latter, then it leaves the vessel by theoutlet 25 provided for this purpose in the inlet compartment 21; thesweeping gas loaded with H₂ S being then directed to an incinerationzone. The liquid sulfur treated is continuously drawn off by the conduit49 mounted on the pump 44 of the spray system 43 that is arranged in theoutlet compartment 41 of the vessel 20.

By way of variation, the operation of spraying the mixture of liquidsulfur and catalytic system provided in the discontinuous process, or atleast one of the spraying operations provided in the continuous process,can be replaced by a stripping operation of the H₂ S by means of aninert gas injected into the liquid sulfur contained in thecompartment(s) of the treatment vessel. In the device of FIG. 1, thecompartment 2 can be eliminated, the liquid sulfur and the catalyticsystem being directly introduced in the compartment 3 which thenconstitutes the only compartment of the vessel.

The invention is illustrated by the examples that follow which arenon-limiting.

EXAMPLES 1 TO 4

In these examples, which are control examples, the H₂ S contained in theliquid sulfur originating from a CLAUS sulfur unit was removed byworking either in the absence of catalyst (example 1) or in the presenceof a catalyst consisting of sodium hydroxide in a 3% solution inn-decanol (example 2) or ammonia (example 4), or also in the presence ofonly one surfactant compound without basic character, namely, theoxyethylated tertiododecyl mercaptan containing 7 ethylene oxide groups(example 3).

The process was carried out in a glass flask kept at constanttemperature in a bath of oil controlled by a thermostat. The flask wasprovided with a first nozzle through which passed a glass dip tube forintroducing a stripping gas, a second nozzle through which passed aglass tube for introducing a sweeping gas, the end of said tube beingsituated approximately two centimeters above the open surface of theliquid sulfur, and a third nozzle for injection of the catalyst and fordrawing off samples of liquid sulfur, said flask having in addition anoutlet for the gases connected to a discharge conduit and a system fortrapping the H₂ S.

In the flask was placed 1 kg of liquid sulfur collected at the exit of asulfur unit condenser, said sulfur was kept at a temperature of 140° C.(examples 1 to 3) or 150° C. (example 4). The process was begun byintroducing into the flask, through the dip tube, 50 l/h nitrogen by wayof a stripping gas and, through the sweeping tube, 1201/h air assweeping gas and from the flask was evacuated by the appropriate conduit1701/h of a gaseous effluent that was directed to the trapping system.At specific intervals, samples of liquid sulfur were removed and theamount of the H₂ S and the sulfanes that they contained were determinedby argentimetry or iodometry. The end point of the determination wasdetected by potentiometer at the accuracy of bimetallic electrodes.

The result of the determination was reported as "total H₂ S" andrepresents the sum of the contents in the liquid sulfur respectively offree H₂ S and of H₂ S combined in the form of sulfanes.

In examples 2 and 3 the catalyst or additive was introduced into theflask by means of a microsyringe through a septum that sealed the thirdnozzle of the flask, at the beginning of the process. The amount ofcatalyst or additive was 50 ppm by weight based on the weight of liquidsulfur. In example 4, there were effected two additions of 25 ppmammonia into the liquid sulfur by addition to the stripping gas, thefirst addition was made at the beginning of the experiment (Duration oftreatment=0) and the second addition at the end of one hour.

The results obtained are shown in Table I.

                  TABLE 1                                                         ______________________________________                                                            DURATION    "TOTAL H.sub.2 S"                                    CATALYTIC    OF          CONTENT OF                                    EX-    SYSTEM or    TREATMENT   THE LIQUID                                    AMPLE  ADDITIVE     (min.)      SULFUR (ppm)                                  ______________________________________                                        1      NONE         0           145                                                               30          133                                                               60          120                                                               90          113                                                               120         103                                           2      Na OH in solution                                                                          0           136                                                  at 3% by weight                                                                            30          128                                                  in n-decanol 60          118                                                               90          108                                                               120         96                                            3                   0           158                                                               30          141                                                  TDM.7 (O.E)* 60          126                                                               90          115                                                               120         85                                            4                   0           465                                                               60          284                                                  NH.sub.3     120         132                                                               240         18                                                                300         9.5                                           ______________________________________                                         *TDM.7 (O.E) = oxyethylated tertiododecyl mercaptan containing 7              (OCH.sub.2 CH.sub.2) groups.                                             

EXAMPLES 5 TO 10

In these examples, the H₂ S contained in the liquid sulfur originatingfrom a condenser of a CLAUS sulfur plant was removed by using acatalytic system according to the invention of the two-component type.

The work was carried out in a device similar to the one used in thecontrol examples and at 140° C. (examples 5 to 8) or 150° C. (examples 9and 10) with a stripping gas rate of 60 l/h (examples 5 to 8) or 100 l/h(examples 9 and 10), the sweeping gas rate was 120 l/h for the differentexamples. The amounts of catalyst system used changed from example toexample.

The nature and quantity of the catalyst system used in each one of theexamples and the results obtained are shown in Table II.

The comparison of the results of examples 5 to 8 with those of thecontrol examples demonstrates the effectiveness of the two-componentcatalytic system according to the invention which makes it possible toobtain "total H₂ S" contents in the liquid sulfur that are less than 10ppm at the end of a period of treatment substantially shorter than thatneeded when using a basic catalyst alone (Control examples 2 and 4) or anon-basic surfactant compound alone (example 3).

                  TABLE II                                                        ______________________________________                                               CATALYTIC    DURATION    TOTAL H.sub.2 S"                                     SYSTEM       OF          CONTENT OF                                    EX-    (nature and  TREATMENT   THE LIQUID                                    AMPLE  quantity)    (min.)      SULFUR (ppm)                                  ______________________________________                                        5      TDM.7 (OE)   0           135                                                  containing 3% by                                                                           15          55                                                   weight NaOH  30          7                                                    50 ppm       45          <1                                            6      TDM.7 (OE)   0           160                                                  containing 3% by                                                                           15          80                                                   weight NaOH  30          13                                                                45          7                                                    25 ppm       60          <1                                            7      TDM.7 (OE)   0           702                                                  containing 3% by                                                                           30          33                                                   weight NaOH                                                                   25 ppm       60          <2                                            8      Nonylphenol.7                                                                              0           150                                                  (OE)* containing                                                                           15          74                                                   in solution 0.6%                                                                           30          25                                                   by weight NaOH                                                                             30          9                                                    30 ppm       45          5                                             9      TDM.7 (OE)   0           473                                                  containing 3% by                                                                           10          263                                                  weight NaOH  30          67                                                                70          31                                                   46 ppm       95          18                                                                120         8.5                                           10     Nonylphenol.7                                                                              0           469                                                  (OE)* containing                                                                           10          56                                                   in solution 0.6%                                                                           20          10                                                   by weight NaOH                                                                50 ppm       30          <2                                            ______________________________________                                         *Ethoxylated nonylphenol containing 7 (OCH.sub.2 CH.sub.2) groups.       

EXAMPLES 11 TO 21

In these examples, the H₂ S contained in the liquid sulfur originatingfrom a condenser of CLAUS sulfur unit was removed by using a catalyticsystem of the mono-component type according to the invention. Thecatalytic system consisted of a compound which has both basic propertiesand surfactant properties.

The work was carried out in a device similar to the one used in thecontrol examples with stripping gas and sweeping gas rates respectivelyequal to 100 l/h and 120 l/h, the nature and quantity of the catalyticsystem and the temperature of treatment changed from one example to theother.

The monocomponent catalytic systems used in the different examples wereselected from the following amino surfactant compounds (commercial namesin parentheses):

(A) - Diamine propylene tallow of the formula R--NH--(CH₂)₃ --NH whereinR represents an aliphatic radical with from C₁₄ to C₂₀ (DINORAM S)

(B) - N, N', N'-polyoxyethylene N-tallow propylene diamine of theformula ##STR6## wherein R represents an aliphatic radical having fromC₁₄ to C₂₀ and x+y+z=7

(C) - Polyoxyethylene tallow amine of the formula ##STR7## wherein Rrepresents an aliphatic radical having from C₁₄ to C₂₀ and (x+y)=7.

(D) - Polyoxyethylene tallow amine of a formula analogous to the onedefined under C) but with x+y=5 (NORAMOX S 5).

(E) - N-bis hydroxy-2 ethyl cocoamine of the formula ##STR8## wherein Rrepresents an aliphatic radical having from C₁₀ to C₁₈ (NORAMOX C2).

(F) - Di-cocomethyl amine of the formula ##STR9## wherein R representsan aiphatic radical having from C₁₀ to C₁₈ (NORAM M2C).

(G) - Di(hydrogenated tallow) dimethylammonium chloride of the formula##STR10## wherein R represents an alkyl radical having from C₁₆ to C₁₈.

(H) - Dimethyl benzalconium chloride of the formula ##STR11##

The specific conditions of the different examples and the resultsobtained are shown in Table III.

The comparison of the results of examples 11 to 21 with those of thecontrol examples clearly shows the effectiveness of the monocomponentform of the catalytic system according to the invention which results invery short treatment time for reducing the "total H₂ S" content ofliquid sulfur below 10 ppm.

                  TABLE III                                                       ______________________________________                                        CATALYTIC      TREATMENT    "TOTAL H.sub.2 S"                                        SYSTEM      Temper-  Dura- CONTENT OF                                  EX-    (nature and ature    tion  THE LIQUID                                  AMPLE  quantity)   (°C.)                                                                           (min.)                                                                              SULFUR (ppm)                                ______________________________________                                        11     A           135      0     452                                                53 ppm               6     33                                                                      18    4                                                                       20    <2                                          12     B           135      0     450                                                46 ppm               4     68                                                                      15    <2                                          13     C           135      0     477                                                49 ppm               4     83                                                                      12    8                                                                       20    <1                                          14     D           135      0     534                                                30 ppm               4     106                                                                     10    24                                                                      17    <2                                          15     D           150      0     504                                                30 ppm               4     182                                                                     12    48                                                                      19    24                                                                      32    <2                                          16     D           165      0     504                                                30 ppm               4     274                                                                     12    173                                                                     30    122                                                                     55    78                                                                      168   <2                                          17     D           135      0     458                                                9 ppm                10    19                                                                      20    <2                                          18     E           150      0     508                                                30 ppm               5     103                                                                     13    20                                                                      22    <2                                          19     F           150      0     529                                                46 ppm               5     111                                                                     13    25                                                                      20    4                                                                       22    <2                                          20     G                    0     451                                                30 ppm      150      6     184                                                                     15    30                                                                      21    10                                                                      30    <2                                          21     H           150      0     510                                                39 ppm               12    50                                                                      20    8                                                                       25    <2                                          ______________________________________                                    

What is claimed is:
 1. In a process for the removal of H₂ S present inliquid sulfur in a dissolved state or combined as hydrogen polysufideswherein a catalyst system comprising at least one basic compound isadmixed with liquid sulfur and the H₂ S is separated from the liquidsulfur, the improvement which comprises including in the catalyst systemat least one surfactant compound which has substantially no basicproperties.
 2. The process of claim 1 wherein the catalyst systemcomprising at least one basic compound and at least one surfactantcompound are added to the liquid sulfur as a mixture.
 3. The process ofclaim 1 wherein the catalyst system comprises at least two componentscomprising at least one basic compound as a first component and at leastone surfactant compound as the second component and wherein the firstand second components are added to the liquid sulfur separately.
 4. Theprocess of claim 1 wherein the catalyst system contains from about 0.05to about 50% by weight of the at least one basic compound.
 5. Theprocess of claim 4 wherein the catalyst system contains from about 0.2to about 20% by weight of the at least one basic compound.
 6. Theprocess of claim 1 wherein the amount of catalyst system added to theliquid sulfur is between about 0.5 to 60 ppm based on the weight of thesulfur.
 7. The process of claim 1 wherein the liquid sulfur is contactedwith the catalyst system at a temperature from about 130° C. to 165° C.8. The process of claim 1 wherein the liquid sulfur containing thecatalyst system is agitated by mechanical agitation means.
 9. Theprocess of claim 1 wherein the liquid sulfur containing the catalystsystem is agitated by spraying the liquid sulfur containing the catalystsystem.
 10. The process of claim 1 wherein an inert gas is introducedinto the liquid sulfur containing the catalyst system whereby the liquidsulfur containing the catalyst system is agitated and the H₂ S isseparated from the liquid sulfur.
 11. The process of claim 8 wherein theopen surface of the liquid sulfur containing the catalytic system isswept with an inert gas to separate the H₂ S from the liquid sulfur. 12.The process of claim 9 wherein the open surface of the liquid sulfurcontaining the catalytic system is swept with an inert gas to separatethe H₂ S from the liquid sulfur.
 13. The process of claim 10 wherein theopen surface of the liquid sulfur containing the catalytic system isswept with an inert gas to separate the H₂ S from the liquid sulfur. 14.The process of claim 1 wherein the surfactant compound comprises atleast one surfactant compound selected from the group consisting ofoxyethylated mercaptans, oxyethylated phenols, polyethylene glycolesters, derivatives of oxyalkyl amides and polyethoxyesters of fattyacids.
 15. In a process for the removal of H₂ S present in liquid sulfurin a dissolved state or combined as hydrogen polysulfides wherein acatalyst system comprising at least one basic compound is admixed withliquid sulfur and the H₂ S is separated from the liquid sulfur, theimprovement which comprises selecting said at least one basic compoundfrom the group consisting of amino surfactants of the formula: ##STR12##wherein R is a C₈ to C₂₂ alkyl or C₈ to C₂₂ alkenyl radical, m, n, p andq are integers of from 1 to 4 inclusive and x, y and z represent anumber of from 1 to 10 inclusive.
 16. The process of claim 15 whereinthe amount of catalyst system added to the liquid sulfur is betweenabout 0.5 to 60 ppm based on the weight of the sulfur.
 17. The processof claim 15 wherein the liquid sulfur is contacted with the catalystsystem at a temperature from about 130° C. to 165° C.
 18. The process ofclaim 15 wherein the liquid sulfur containing the catalyst system isagitated by mechanical agitation means.
 19. The process of claim 15wherein the liquid sulfur containing the catalyst system is agitated byspraying the liquid sulfur containing the catalyst system.
 20. Theprocess of claim 15 wherein an inert gas is introduced into the liquidsulfur containing the catalyst system whereby the liquid sulfurcontaining the catalyst system is agitated and the H₂ S is separatedfrom the liquid sulfur.
 21. The process of claim 18 wherein the opensurface of the liquid sulfur containing the catalytic system is sweptwith an inert gas to separate the H₂ S from the liquid sulfur.
 22. Theprocess of claim 19 wherein the open surface of the liquid sulfurcontaining the catalytic system is swept with an inert gas to separatethe H₂ S from the liquid sulfur.
 23. The process of claim 20 wherein theopen surface of the liquid sulfur containing the catalytic system isswept with an inert gas to separate the H₂ S from the liquid sulfur. 24.The process of claim 15 wherein the amino surfactant catalyst consistsessentially of at least one compound of the formulae ##STR13##
 25. Acomposition of matter consisting essentially of liquid sulfur issuedfrom a CLAUS process containing based on the weight of the liquid sulfurbetween 0.5 to 60 ppm of a catalytic system consisting essentially of amixture of at least one basic compound and at least one surfactantcomponent which has no substantial basic character.
 26. The compositionof claim 25 wherein said at least one surfactant component is selectedfrom the group consisting of oxyethylated mercaptans, oxyethylatedphenols, polyethylene glycol esters, oxyalkylamide derivatives andpolyethoxyesters of fatty acids.
 27. The composition of claim 25 whereinthe basic component and the surfactant component are combined inproportions such that the amount of basic component represents from 0.05to 50% by weight of the components.
 28. The composition of claim 27wherein the catalyst system contains from about 0.2 to about 20% byweight of the at least one basic compound.
 29. A composition of matterconsisting essentially of liquid sulfur issued from a CLAUS process andcontaining based on the weight of the liquid sulfur between 0.5 and 60ppm of a catalyst system consisting essentially of at least one basiccompound selected from the group consisting of the amino surfactants ofthe formula: ##STR14## wherein R is a C₈ to C₂₂ alkyl or C₈ to C₂₂alkenyl radical, m, n, p and q are integers of from 1 to 4 inclusive andx, y and z represent a number of from 1 to 10 inclusive.
 30. Thecomposition of claim 29 wherein said amino surfactants are of theformula ##STR15##
 31. A mixture consisting of liquid sulphur, H₂ Spresent in the liquid sulphur, in a dissolved state and combined ashydrogen polysulfide, at least one basic compound and at least onesurfactant which has no substantial basic character.
 32. A mixture ofclaim 31, wherein the at least one surfactant is selected from the groupconsisting of oxyethylated mercaptans, oxyethylated phenols,polyethyleneglycol esters, oxyalkylamide derivatives andpolyethoxyesters of fatty acids.
 33. A mixture of claim 31, wherein theamount of the basic compound represents from 0.05 to 50% by weight ofthe amount of basic compound and surfactant in the mixture.
 34. Amixture consisting of liquid sulphur, H₂ S present in the liquidsulphur, in a dissolved state and combined as hydrogen polysulfide, andat least one basic compound selected from the group consisting of aminosurfactants of the formula ##STR16## where in R is a C₈ to C₂₂ alkyl orC₈ to C₂₂ alkenyl radical, m,n,p and q are integers of from 1 to 4inclusive and x,y and z represent a number of from 1 to 10 inclusive.35. The composition of claim 34, wherein said amino surfactants are ofthe formula ##STR17##